1. Field of the Invention
Embodiments of the present invention relate to a performance data generation apparatus, and more particularly to a performance data generation apparatus including a guitar synthesizer that generates performance data, such as MIDI (music instrument digital interface) signals based on performance signals provided by a stringed instrument or the like.
2. Description of Related Art
A conventional guitar synthesizer detects string vibrations of a stringed instrument, such as a guitar, and generates performance data representative of string vibration signals based on the detected string vibrations. MIDI signals are generated based on the performance data, and used to drive a sound source apparatus. The sound source apparatus generates tones having tone colors, pitches and tonal strength (velocity) based on the performance.
As a typical acoustic characteristic of a guitar which is a plucked instrument, a tone (or a string vibration) that is generated upon playing the guitar string has an envelope that rapidly rises and attenuates. As a result, the time duration of a tone that is generated by the guitar is relatively short.
In order to generate a tone that lasts for an extended period of time with a guitar, a guitar synthesizer is provided with a performance mode that uses a sustain pedal or a hold pedal. Generally, the sustain pedal or the hold pedal is provided as a pedal switch that is connected to the guitar synthesizer and is operated by the performer's foot.
FIGS. 10 (a) and 10 (b) show an example of a conventional performance method in which a sustain pedal is used. More specifically, FIG. 10 (a) schematically shows envelopes of string vibrations representative of performance notes that are played by a performer (herein after referred to as notes). FIG. 10 (b) schematically shows envelopes of sound source output notes having a predetermined tone color. The sound source output notes are generated based on performance data representative of the string vibrations shown in FIG. 10 (a) and outputted by a sound source apparatus of a guitar synthesizer.
For example, as shown in FIG. 10 (a), when the performer plays a note A at time t1, the guitar synthesizer generates a corresponding MIDI signal of note-on data. As shown in FIG. 10 (b), a sound source output note As is generated by the sound source apparatus at a time corresponding to time t1. The sound source output note As has a pitch and a velocity corresponding to those of the note A.
In this case, the performer operates the sustain pedal at time t2 while the note A is still in a note-on state, as shown in FIG. 10 (a). In response to the operation of the sustain pedal, the guitar synthesizer starts a sustain mode at time t2.
For example, when the sustain mode is started, a sound source output note that is generated by the sound source apparatus is controlled so that the sound source output note is gradually attenuated at a specified sustain rate that is pre-set for the tone color of the sound source output note. In other words, even when vibration of the note A shown in FIG. 10 (a) substantially stops at time t3, and accordingly note-off data for the note A is generated, the guitar synthesizer invalidates the note-off data and the sound source output note As is sustained at the sustain rate so that the tone generation of the sound source output note As is continued. As a result, even when a note originally played by the guitar attenuates to zero level, the sound source output note is continuously generated by the sound source apparatus for an extended period of time, substantially longer than the note originally generated by the guitar.
In this example, the performer plays a note B at time t4 as shown in FIG. 10 (a). The guitar synthesizer generates a sound source output note Bs by the sound source apparatus having the same tone color of the sound source output note As based on note-on data representative of the note B, using a tone generation channel which is different from the one used for the sound source output note As. In this example, the sustain mode is maintained to be turned on even after the note B is played. As a result, note-off data for the note B is likewise invalidated when the note B completely attenuates at time t5. As a consequence, in addition to the sound source output note As which has been previously generated and is sustained, the sound source output note Bs is also sustained at a predetermined sustain rate. Accordingly, after time t4, the sound source output notes As and Bs are concurrently outputted until the sound source output note As completely attenuates.
By using the above-described operation, a note A and a note B having different pitches may be played concurrently to form a chord that lasts for a substantially extended period of time which may be impossible to attain by an ordinary guitar performance. Also, an ordinary guitar has six strings and therefore a chord containing more than six notes cannot be performed by an ordinary performance method. However, the sustain mode allows many more notes to be successively superposed. As a result, a chord containing seven or more notes can be readily formed, depending on the number of tone generation channels.
FIGS. 11 (a) and 11 (b) show an example of a conventional performance method in which a hold pedal is used. More specifically, FIG. 11 (a) schematically shows string vibrations representative of notes played by the guitar, and FIG. 11 (b) schematically shows envelopes of sound source output notes that are outputted from the sound source apparatus of the guitar synthesizer according to MIDI signals which are generated based on the string vibrations.
For example, when a hold mode is started by the operation of the hold pedal, the tone generation is controlled so that note-off data for a note is invalidated and a sound source output note corresponding to the note is sustained, which is similar to the sustain mode described above. However, in the hold mode, the sustain operation is continued until the hold mode is canceled.
Further, in the hold mode, a sound source output note that is generated based on newly provided note-on data uses a MIDI channel that is different from a MIDI channel used by a sound source output note that has been previously generated.
More particularly, when a note A is played at time t1 shown in FIG. 11 (a) after the hold pedal is operated to start the hold mode, note-on data for the note A is provided. As a result, a sound source output note Ah representative of the note A is generated as shown in FIG. 11 (b). Since the sound source output note Ah is currently sustained in the hold mode, note-off data for the sound source output note Ah is ignored even when the note A attenuates, for example, at time t2. Then, a new note B is played at time t3, and a sound source output note Bh representative of the note B is generated.
As described above, the sound source output note Bh is generated using a MIDI channel that is different from the one used for the previously generated sound source output note Ah. Also, the sound source output notes are sustained until the hold mode is removed.
The performance in the hold mode provides a variety of acoustic effects. For example, a chord containing notes that last for an extended period of time is readily provided, which is similar to the acoustic effect provided by the sustain mode. Furthermore, different tone colors may be assigned to MIDI channels that are respectively used by the sound source output notes Ah and Bh. Consequently, a chord including different tone colors is obtained, resulting in an acoustic effect that assimilates a performance by a plurality of different pieces of musical instrument.
Now, let us consider one of the performance methods desired to be achieved by a guitar synthesizer in which one tone color is generated for an extended period of time by using a sustain mode or a hold mode, and pitch variation (pitch bend) is optionally added to the tone color that is sustained.
There are a variety of performance methods to add pitch variation to a note that is generated upon picking or strumming the guitar string, such as, for example, a slide performance method, a choking performance method, an arming performance method and the like. In the slide performance method, after a note is played by picking the guitar string, the performer slides the finger that depresses the guitar string from one fret to another with the string being continuously depressed by the finger. In the choking performance method, the guitar string that is depressed by the finger is pulled in a direction along the finger plate to change the tension of the guitar string to raise the pitch. Also, a vibrato unit is used to change the pitch of the guitar string in the arming performance method. The vibrato unit typically includes a bridge for supporting the guitar strings that is rotatable about a pivot, and an action member, known as an arm, for moving the bridge to thereby change the pitch of the guitar string. Tones of the guitar strings that are changed by one of the above-described methods are converted to MIDI pitch bend data by the guitar synthesizer to control pitches of sound source output notes.
However, the above-described performance methods and intended effects are very difficult to achieve when either the sustain mode or the hold mode described above with reference to FIGS. 10 (a) and 10 (b) or FIGS. 11 (a) and 11 (b), respectively, is used.
For example, in the case of the sustain mode, a note A is played at time t1 shown in FIG. 10 (a) to start a note-on state, and the sustain mode is started at time t2. As a result, as described above, a sound source output note As is generated and sustained at a specified sustain rate as shown in FIG. 10 (b). However, pitch bend control over the sound source output note As is only possible until the note A completedly attenuates, as shown in FIG. 10 (c). In other words, even though the performer adds pitch variation to the note A by using one of the performance methods described above, the pitch variation in the note A is reflected in the sound source output note As until time t3 when the note A attenuates and comes to a note-off state, as shown in FIG. 10 (c). Accordingly, during the period between t1 and t3, the note A or the pitch variation in the note A is detected and a MIDI signal for pitch bend data representative of the pitch variation in the note A is outputted, and therefore the pitch bend control over the sound source output note As can be performed. However, when the note A comes to a note-off state at time t3 and thereafter, pitch bend data for the note A is not provided. As a result, the pitch is fixed based on pitch bend data that is obtained immediately before time t3 and the sustain operation is continued, and therefore further pitch bend control over the sound source output note As cannot be performed beyond time t3.
Let us assume that the performer then plays a note B at time t4 by picking at the same string that generates the note A in an attempt to add pitch variation to the sound source output note As shown in FIG. 10 (a). By such a performance by the performer, a new sound source output note Bs is generated at a time corresponding to time t4, using a different tone generation channel, as described above. As a result, two of the notes are superposed with one another. It is noted that no pitch bend control over the sound source output note is available during the period between time t3 and time t4, as shown in FIG. 10 (c).
When the performer adds pitch variation to the note B in the state described above, pitch bend is added to both of the sound source output notes As and Bs because the sound source output notes As and Bs are generated by the same MIDI channel and therefore pitch bend data is effective to both of the sound source output notes As and Bs. In some cases, the sound source output notes As and Bs may form a dissonant chord that is not desired by the performer.
Therefore, in the sustain mode operation shown in FIGS. 10 (a) and 10 (b), the pitch bend control cannot be continuously performed on a sound source output note while the sound source output note is sustained. Also in the hold mode operation shown in FIGS. 11 (a) and 11 (b), the pitch bend control likewise cannot be continuously performed on a sound source output note that is placed in the hold mode.